On Jan. 21, the Minneapolis (Minnesota) City Council again voted to approve a solar project on top of the city’s convention center that would provide about 5 percent of the power the facility uses.
The newest deal, aimed at St. Paul, Minnesota-based Best Power International LLC, a design-build solar energy company owned by Mario Monesterio, intends to provide a 600-kilowatt rooftop solar photovoltaic system delivered via 2,600 solar panels installed on the flat portions of the convention center roof to prevent obscuring the building’s signature domes.
The size of the installation is estimated at about four football fields, and would be twice as large as the solar photovoltaic energy system installed at St. John’s Abbey in October of 2009, which is currently the largest solar array in Minnesota.
This is the second time the city council has pushed the convention solar project. The first time – in the summer of 2009 – would have seen the system installed by Boulder, Colorado-based EyeOn Solar LLC, but the deal fell through in late June when the city council voted to sever all ties with the solar developer because the two (company and city council) could not agree, and EyeOn could reportedly not meet deadlines.
This cautious attitude was heightened by council member Lisa Goodman, who said she was reluctant to don the “happy environmental hat” at the drop of a hat, figuratively speaking, even though the project needed to be completed in December in order to take advantage of federal incentives. This incentive, offered as a CREB, or clean renewable energy bond, was set to expire at the end of 2009 but was subsequently renewed.
Even with the new local provider, Best Power (local being one of the stipulations of the original grant), the project still faces the eagle eye of the Minnesota Public Utilities Commission, or MPUC, which must vote to move the $2-million renewable energy grant into the city’s coffers to help subsidize the deal – which requires some matching funds.
The final vote by the city council, to name Best Power as preferred provider, is scheduled for Jan. 29. Assigning the $2 million to the city seems assured. The only question city residents have is how effective solar panels are likely to be on a flat roof, given Minnesota’s winter snowfall.
Minneapolis’ average solar insolation value is 3.5 (on a scale of 2.5 to 6.5 in the continental U.S.), and it averages about 2,800 hours of sunshine a year – compared to Arizona’s 3,600 hours, but the state’s overall cooler temperatures may be a definite asset to solar energy, since conventional silicon solar panels tend to become less efficient at converting radiation once the ambient temperature exceeds a certain threshold.
In fact, an experiment in Britain showed efficiencies dropping 40 percent at anything over 105 degrees (Fahrenheit). Another study, on roofs, showed that – at a relative daytime temperature of 75 degrees (Fahrenheit) – the roof temperature was 157 degrees, and it’s well known among building contractors that a 90-degree summer day can produce non-reflective (asphalt shingle, tile) roof temperatures of more than 160 degrees.